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Everything you need to know about AdBlue

Published 19 June 2017

We get a lot of questions from readers about Adblue. What it is, which cars use it and why is it needed? So we've compiled this guide to answer some of the most commonly asked questions.

To comply with Euro6 regulations, car manufacturers have had to focus on minimising harmful nitrogen-oxide emissions (NOx) - which are a major source of atmospheric pollution that causes smog in urban centres. 

AdBlue technology is used in newer diesel vehicles to help reduce exhaust emissions. Fortunately, filling your AdBlue tank is a relatively simple process.

What is AdBlue and how does it work?

AdBlue is a non-toxic, colourless solution of urea and water-based fluid. It works with what's called Selective Catalytic Reduction (SCR) to bring diesel engines up to the standard required to meet Euro6. 

SCR works with AdBlue to convert NOx emissions from the engine into nitrogen and water. It’s used by many carmakers - including Audi, BMW, Volkswagen, Peugeot, Citroen and Mercedes-Benz.

Does my car use AdBlue?

Only recently built, diesel cars will have AdBlue systems fitted and many people are unaware the system is installed until a warning message appears. Most cars have the AdBlue filler located near the fuel cap, however some models have them hidden beneath the boot carpet. If in doubt, consulting the owner's handbook will clear things up.

When do I need to refill my AdBlue?

If you cover more miles than most, you may find that you need to refill your AdBlue more regularly. When the tank is getting low, you'll receieve a warning light on the dash reminding you to top it up. If the tank runs dry, the car won't start.

Most vehicles also require a minimum amount is added in order to remove the warning message, but these vary from car to car. AdBlue will eventually degrade over time, lasting about 12 months. But in the unlikely event of that happening, you'll get warning message on the dash.

Should I do it myself?

Like our Keith, you can leave the car until it runs out of AdBlue and then take it to a dealer to refill. In that instance, the dealer was the cheaper and easier option.

However, you can do it yourself. Just open the AdBlue filler cap, attach the filling nozzle and pour it into the tank. Some cars require that you use the wheel brace to undo the AdBlue filling cap, so - again - check the owner's manual beforehand.

How much does it cost?

Look on eBay and you'll find 20-litres for about £20, but you may also need to purchase a filling nozzle (another tenner). Or a 10-litre bottle from Halfords is £14.

How much AdBlue will my car use?

AdBlue consumption varies from vehicle to vehicle (a Volkswagen Passat gets through about 1.5-litres every 620 miles). But - like fuel consumption - the faster you drive, the more AdBlue you'll burn through.

Most AdBlue tanks hold around 10-litres or more, so most average drivers will find that AdBlue - like screenwash - will be topped up at the annual service.

>> Everything you need to know about DPFs

>> All you need to know about your right to reject a car


   on 19 June 2017

My 2016 Landover Discovery Sport uses AdBlue but to do this the fuel tank capacity has been reduced. When towing our caravan I don't get 250 miles to a tank full. How did this version win Tow-car of the year being so restricted?

footsfitter    on 19 June 2017

Just about to order some for this harvest- new combine last year is the 1st machine the farm has owned with ad-blue, used 800L last summer!

Refuelling the 1287L fuel is daily, not unusual to burn 3/4 tank in 12hrs and the 159L ad-blue tank lasts every 2nd or 3rd re-fuel. For us keeping Ad-blue clean in a dusty refuelling environment is a priority given the tiny yet expensive filter in the system.

You need to be super careful not to spill it as it is highly corrosive and crystallizes to leave a salt like residue.

NickNike    on 19 June 2017

By how much does the lethal NOx get reduced by?

Mike Lanc    on 19 June 2017

Oxides of nitrogen only pose a significant risk in areas of congestion and very slow moving traffic. Would it not therefore be sensible to limit Adblue injection to situations where the road speed is say less than 20 mph? If I am not mistaken, that is similar to what VW did in the US. It is a sad case of regulation overruling common sense.

SteveTTT    on 19 June 2017

My new in September 2016 Jaguar XF came up with its first low Adblu warning of 1500 miles left after only 4000 miles which included a recommended running in period. This in a 180ps car with a 17 litre DEF tank driven on mainly motorway miles. Jaguar's website currently suggests a range of 8000 miles, however the dealer when challenged suggested it should do 10000+ miles! Another case of unattainable efficiency statistics based on unrealistic government test requirements? In reality a further tax on diesel drivers. Will be interesting to see if/how these numbers change when the new "real world" efficiency tests come in.

Edited by SteveTTT on 19/06/2017 at 21:21

Phil Norton    on 20 June 2017

The only clean diesel is a scrapped one.

Chris James    on 23 June 2017

Better scrap your petrol too, given modern Direct Injection Petrol cars are just as polluting as Pre-DPF Diesels. In fact, at least one EU6 Petrol was found to emit far more dangerous particles than an older EU5 Diesel.

Hope the motoring journalists are aware of this fact, I 'm sure they wouldn't want to be seeing to be persuading people to leap out of one problem, straight into another and one which may very well be next in line to be heavily taxed and banned from cities. There is already talk of fitting particulate filters to petrol cars, (with VW already in the process of doing it), a fact which adds more than a degree of integrity to the Science article linked to. Once the sheeple have all faithfully swapped their diesel cars for a new direct injection petrol, guess which will be next in the tax crosshairs!, and so the circle continues.

Edited by Chris James on 23/06/2017 at 19:00

Alan Pearson    on 22 June 2017

Urea is synthetic in add blue made up from ammonia and carbon dioxide, two harmful substances.

BikerGSA    on 22 June 2017

Adblue has been used for some time now in the heavy haulage industry and car drivers should be warned that Adblue is corrosive to aluminium alloys and some other metals like the "copper" in wiring for example - whenever using Adblue always think plastic for transporting and using and immediately wipe off any spillage from wherever. Adblue will also crystallize over a period of time so best not leave a vehicle for long periods without using it for whatever reasons.

People have been known to consider adblue as a fuel additive, it is most definitely not with on trucks it being sprayed into the final exhaust system.

The system can be easily and accidently contaminated with other fluids for example washer fluid and some soap solutions for vehicle wash which are similar in colour so always keep stored adblue well labeled and away from other similar coloured fluids. The cost of repair to contamination on trucks is very expensive so is likely to be the same on cars also, occasionally having the whole system replaced.

This, by the way, is all from previous workshop experience.

beatbox    on 27 October 2017

Do any of your avid readers and contributors have any thoughts on using LPG ?
LPG and cars using it are available across Europe.
But why not here?
Firstly, I would like to see every petrol station be forced to stock LPG, so that it can be readily available.
At least it would be a start.

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